Alleviating the Adverse Effects of Drought Stress on Physiological Characters of Filed Pumpkin by Salicylic Acid and Selenium

Field pumpkin (Cucurbita pepo) is a widely consumed herbaceous vegetable valued for its nutritional and medicinal properties. This study aimed to investigate the effects of field applications of selenium (Se; 0 and 3 mg/L) and salicylic acid (Sa; 0, 0.7, and 1.5 mM) under varying drought stress levels (25, 55, and 80% field capacity) on the physiological traits and seed yield of field pumpkin. Results indicated that drought stress adversely affected the content of photosynthetic pigments (chlorophyll a, chlorophyll b, total chlorophyll, and more polar carotenoids), antioxidant enzyme activities (catalase, peroxidase, and ascorbate peroxidase), proline levels, relative water content (RWC), and malondialdehyde (MDA) accumulation. The individual and combined application of Se and Sa significantly enhanced the content of photosynthetic pigments, activated antioxidant enzymes, improved proline content and RWC, and reduced MDA levels. Notably, at 80% drought stress, seed yield decreased by approximately 51% compared to conditions at 25% filed capacity. Across all drought levels, the application of 1.5 mM Sa, with or without Se, was identified as the most effective treatment for increasing seed yield, while the majority of physiological traits were optimized with 1.5 mM Sa combined with 3 mg/L Se. This study enhances our understanding of the physiological mechanisms by which selenium and salicylic acid improve the resilience of field pumpkin production in arid and semi-arid regions, contributing to more sustainable agricultural practices under water-limited conditions.